Yes, when making unscented soap. I typically use a 33% solution. That's 2 parts water and 1 part lye, or 1/3 of the solution is lye, hence the 33%. When I'm making a batch of soap with no FO to speed things up, like Castille, I've used even higher percentages. Thinking about the "lye heavy" statement. It makes me wonder...How much water does lye need to fully dissolve? Will it fully dissolve in a 50% solution or is that what you mean by a 40% solution being lye heavy.